> Even though I click on refresh button on my client, or even decide to
> delete Temporary Internet Files, or even try to access the updated web
> site from another client, still updated objects (graphics) are served
> from the squid cache, instead of being retrieved again from the server:
>
> 1013688716.387 3 192.168.1.1 TCP_IMS_HIT/304 206 GET
> http://www.example.com/sample.gif - NONE/- image/gif

Yes? You are using transparent proxying, and this breaks valid
assumptions made by your IE browser.

Squid-2.4 has a workaround to the issue with transparent proxying that
one can enable, at the expense of a significant drop in hit ratio for IE
users..